The inner layer of a conventional entrained flow gasification furnace using a coal-water slurry as a raw material is usually formed from a refractory brick, it is required that the ash fusion point (FT) of the coal used as the raw material is not more than 1400 degrees centigrade, thus restricting the choice of the type of the coal. For example, the coal-water slurry gasification furnace of GE requires that the ash fusion point (FT) of the raw material coal is not higher than 1350 degrees centigrade. Accordingly, the conventional gasification furnace limits the use of raw materials, and the cheap coal can not be used widely, so that the application of the conventional gasification furnace is limited. Moreover, the production, mounting, maintenance and replacement of the refractory brick are extremely complex and take much time and effort. In addition, the conventional gasification furnace is poor in cooling effect and high in cost.